(1) Field of the Invention
The present invention pertains to a supporting holder and heat sink for high performance, light emitting diode warning lights. In particular, the present invention pertains to a support casing for light emitting diode warning lights and their optics, where the light emitting diodes and optics are removably held to the support casing by a spring brace and where the support casing functions as a heat sink for the light emitting diodes.
(2) Description of the Related Art
Since the invention of the rotating beacon in the 1940's, a large number of emergency and service vehicles have been protected by warning lights that use an incandescent lamp. In these systems, the lamp is given the appearance of flashing by a rotating reflector positioned in the warning light. The reflector is rotated about the lamp and produces a rotating, reflected arc of coverage and a level of warning within a specified zone around the vehicle.
More recently, emergency and service vehicles have employed warning signal lights comprising light emitting diodes (LEDs). In most emergency warning light applications employing LEDs, it is necessary to use an optic placed in front of the LED. The optic, typically a lens and reflector, focuses the light output of the LED and concentrates and directs the light output into the particular area needed to provide visual protection to the emergency vehicle. Therefore, a typical emergency warning light assembly is comprised of a mounting structure, the LED, and the optic in proper alignment.
At the present time, some of the highest performance, commercially available light emitting diodes are built on circuit boards incorporating an aluminum base. The aluminum base permits cooling of the LED chip by conduction of the heat generated by the LED chip through the aluminum base to a metallic mounting structure. LED assemblies of this type are commonly called “stars” because of the star shape of the aluminum base. The cooling of the LED chip is critical to the operation of the emergency warning light because the light output of the LED is substantially reduced as the temperature of the LED chip increases. In addition, the LED chip could suffer terminal failure at about 105° C.
Since the beginning of the use of light emitting diodes in emergency vehicle warning lights, their performance has continuously improved and is currently at or above 55 lumens per watt for colors such as red-orange. It has been observed that, given the forward voltage requirement of about 3 volts per LED and the voltage drop through the control electronics of a typical warning signal light, a string of LEDs in series is typically used to achieve maximum electrical efficiency on a 12 volt automotive electrical system. LEDs with a 1-watt rating typically operate at 350 milliamps. Thus, in a 12-volt automotive electrical system, the same electrical energy is required to operate one LED, two LEDs connected in series, or three LEDs connected in series. For emergency vehicle applications, it is therefore desirable to employ two or three LEDs connected in series in the warning signal lights of the vehicle. However, with the LEDs connected in series, if one of the LEDs goes out, the other LEDs go out as well. Given the substantial cost of each LED, currently between $5.00 and $10.00 apiece, it is very desirable to be able to replace, in the field, a single failed LED of a series string of LEDs in an emergency vehicle warning signal light.